I'm not an expert, but it sounds like the nuts on the end of the body aren't tightened enough.

1). Remove the dust cover (the rubber bit) using a small flat head screwdriver.
2). Loosen the first nut you see
3). Remove the locknut
4). tighten the next nut you see
5). Put everything back

See if that works. You might want to regrease everything while you're there.